The design of an indoor acoustic environment positively perceived by building occupants requires a perceptual approach to be adopted in order to define what makes it sound good. Soundscape standards ISO 12913 have been introduced to assess how the acoustic environment is perceived, in context, by people. According to the standards, a straightforward characterization of a soundscape as positive is currently possible only through measurements by persons, because of a current gap in linking perceptual metrics to acoustic or psychoacoustic measurements. In addition, despite applying also to indoor contexts, methods and perceptual metrics described by the standards have been mainly derived from studies related to outdoor urban environments and it is not clear whether they could be directly applied indoor. For this reason, a systematic review was performed to investigate: (i) Data collection methods used in the literature for indoor residential soundscapes and (ii) factors, output of such methods, that characterize them positively. For this purpose, a systematic review has been conducted in accordance with the PRISMA guidelines (preferred reporting items for systematic reviews and meta-analyses) guidelines. The Scopus database was searched for peer-reviewed journal papers published in English, between 1 January 2009 and 24 June 2019, including: (1) field or laboratory studies relevant to residential buildings and (2) studies assessing factors that influence the perception by building users of indoor acoustic environments. The search excluded studies related to: (a) Speech perception issues; (b) noise-induced sleep disturbance; (c) acoustic perception by hearing impaired building users; (d) perception of vibrations or impact sounds. The search returned 1087 results. After the screening process, 37 articles were finally included. Given the differences in methodologic approaches, a quantitative meta-analysis could not be performed, and a qualitative approach was adopted instead. A large part of the selected literature reflected a general effort of minimizing noise annoyance by reducing noise exposure and, in particular, noise levels. Questionnaires and guided interviews were used to capture people’s perception, while the adoption of soundwalks and non-participatory behavioral studies did not emerge in the review literature and need further investigation. The evaluation of a variety of auditory sensations both in their positive and negative dimensions, beyond annoyance, would be required to explore the positive perceptual potential of sounds. Besides sound level, a variety of factors related and unrelated to the acoustic environment were found to affect perceptual outcomes and a framework of evaluation has been proposed as a reference for future assessments. Results encourage the integration of soundscape methodologies into IEQ research, in order to enhance user health and well-being.

The focus of the building industry and research is shifting from delivering satisfactory spaces to going beyond what is merely acceptable with a wave of new research and practice dedicated to exploring how the built environment can support task performance and enhance people’s health and well-being. The present study addresses the role of acoustics in this paradigm shift. Indoor soundscape research has recently emerged as an approach that brings a perceptual perspective on building and room acoustics in order to shape built environments that “sound good” according to building occupants’ preference and needs. This paper establishes an initial discussion over some of the open questions in this field of research that is still in an embryonic stage. A thematic analysis of structured interviews with a panel of experts offered a range of perspectives on the characterization, management, and design of indoor soundscapes and health-related outcomes. The discussion pointed out the importance of both perceptual and multisensory research and integrated participatory design practices to enable a holistic view regarding the complex building–user interrelations and the design of just cities. Soundscape methodologies tailored to the peculiarities of indoor soundscapes can help to measure and predict the human perceptual response to the acoustic stimuli in context, thus reducing the risk of mismatches between expected and real building experiences. This perceptual perspective is expected to widen the scientific evidence for the negative and positive impacts of the acoustic environment on human health, well-being, and quality of life. This will support prioritizing the role of acoustics in building design and challenge many current design practices that are based on a noise control approach.

The indoor-outdoor connection provided by ventilation openings has been so far a limiting factor in the use of natural ventilation (NV), due to the apparent conflict between ventilation needs and the intrusion of external noise. This limiting factor impedes naturally ventilated buildings meeting the acoustic criteria set by standards and rating protocols, which are reviewed in this paper for residential buildings. The criteria reflect a general effort to minimize noise annoyance by reducing indoor sound levels, typically without a distinction based on a ventilation strategy. Research has developed a number of solutions, discussed here, that try to guarantee ventilation without compromising façade noise insulation, but, currently, none have been adopted on a large scale. This concept paper highlights the main limits of the current approach. First, a fragmented view towards indoor environmental quality has not included consideration of the following acoustic criteria: (i) how buildings are designed and operated to meet multiple needs other than acoustical ones (e.g., ventilation, visual, and cooling needs) and (ii) how people respond to multiple simultaneous environmental factors. Secondly, the lack of a perceptual perspective has led acoustic criteria to neglect the multiple cognitive and behavioral factors impinging on comfort in naturally ventilated houses. Indeed, factors such as the connection with the outside and the sense of control over one’s environment may induce “adaptive acoustic comfort” opportunities that are worth investigating. The mere use of different sound level limits would not be enough to define criteria tailored to the complex user–building interaction that occurs under NV conditions. More holistic and human-centered approaches are required to guarantee not only neutrally but even positively perceived indoor acoustic environments. For this reason, this paper considers this apparent conflict from a soundscape viewpoint, in order to expose still unexplored lines of research. By underpinning a perceptual perspective and by contextualizing it, the indoor soundscape approach provides a framework capable of overcoming the limits of the traditional noise control approach. This could provide the opportunity to foster a wider adoption of NV as a passive design strategy that enhances user health and well-being, while enabling low-cost, and low-energy cooling and ventilation, thereby contributing to current climate change challenges.

The period of home confinement during the COVID-19 pandemic made the importance of a high-quality surrounding environment even more evident than before. Several studies have been carried out to assess the (negative) impacts of noise on annoyance, particularly whilst working from home (WFH). The present study takes a step further by (1) investigating the positive and negative impacts of the “actual” acoustic environment on a range of activities, i.e., WFH, relaxation, physical, and sexual activities, and (2) identifying the characteristics of an “ideal” indoor soundscape. The study is based on the qualitative analysis of verbal descriptions collected from open-ended questions included in a survey administered in January 2021 to 464 respondents living in London, during the COVID-19 lockdown. The range of impacts in the actual scenario varied from no effect on task execution, to disruption, distraction, concern of disturbing others or being heard. Positive impacts included support of concentration, relaxation, motivation, freedom of sound expression, feeling of being connected to the surroundings and comforted by the presence of others, according to mechanisms described in the study. Negative appraisal could trigger coping strategies (e.g., controlling windows, playing music, wearing headphones) and behavioural changes (e.g., lowering the volume of the voice or music, muting oneself during call, changing workout type) that could in turn limit or enhance the freedom of behaviour, affect or foster wellbeing. Negative impacts were most frequently reported on WFH (by 55% of the participants), followed by relaxation activities (40.6%), sexual activities (30.1%), and home workout (20.1%). The ideal soundscape was described as a quiet, well-sound insulated environment, which guarantees access to positive sounds (i.e., natural sounds, music, urban background), thus resulting in privacy, intimacy, and a place where to express themselves without noise-related constraints. The study complements literature findings on housing design directions in light of the COVID-19 pandemic, by providing further evidence on the impacts of poor sound insulation at home, the potential benefits of nature-based solutions for positive indoor soundscapes, and opportunities for an activity-based design of domestic environments, inclusive of a broader set of home uses and household compositions.